Process for converting hydrocarbon gases



Aug. 31, 1948. L. P. EVANS v 52, 8

PROCESS FOR CONVERTING HYDROCARBON GASES Filed July 16, 1946 FAQ/sans s/1mg -1 FUEL'fl/R 9/ -97 1 was/nu:

Z5 "29 v AUTOMATIC OIL s. v v v. 6 -75 WATER INVENTOR LOUIS P. EVAN o fl w ATTORN Y temperatures onthe order of 1500 Patented A 31,1948

PROCE S FOR CONVERTING HYDRO- CABBON GASES Loni: P. Evans, Woodbury, N. 1., ascignor to So.-

cony-Vacuum Oil Company, Incorporated, a

This invention relates to process and appara tus for cracking hydrocarbons by contact with a highly heated granular solid heat transfer agent. More particularly, the invention is concerned with contacting a hot granular heating agent with two successive types of charge hydro- I carbons of decreasing refractory nature and controlling the contacting process.

Hydrocarbons may be readily converted to high yields of gaseous olefins by reaction at elevated F. and above for very short reaction periods. .Crude peroleum and gas oils are readily converted at 1500 to 1600 1'. using reaction times on the order of 0.2 second. The more refractory hydrocarbons such as propane and ethane require higher'temperatures running up to 1800 to 2000 F. for satisfactory yields. by passing a granular solid heattransfer agent in a cyclic manner through a heater and thence through a reaction contactor wherein the hydrocarbons are passed through a substantially compact moving bed of highly heated granular solid. In conducting the .process for conversion of the more refractory hydrocarbons, the problem of recycling to the heater may present very important practical diiiiculties since existing elevators will not operate satisfactorily in conveying solids at temperatures of theorder of 1500 F. The granular solid discharged from contact" with j ethane does therefore require chilling as by I spraying water or steam thereon to bring it down to satisfactory elevated temperatures.

According to the present invention, a hot granular solid is used for cracking successively less refractory hydrocarbon charge materials to thus bring its temperature down to tolerable levels. The invention is particularly concerned with means for controlling the several reaction zonesto maintain the system in suitable balance. According to the invention, the pressures existing on either side of a line of demarkation between two reaction zones are used to control operation The process is advantageously conducted of the process and thus maintain substantially no pressure drop across the line of demarkation between the two zones.

According to a preferred embodiment of the invention, this is accomplished by automatic control of the back pressure on discharge ports.

from the adjacent zones as shown in the annexed drawing which represents diagrammatically, a system for the cracking of hydrocarbons to produce ethylene and the like.

Agranular solid heat transfer material such as fused alumina pellets of about 0.3 inch in diamtween the two zones.

eter is heated in a heater l by combustion of fuel and air supp ied through line 2, the line gases being withdrawn by 3 and conveyed to a suitable stack or economizer. The granular solid at a temperature of about 1800 to 2000" I". is

transferred downwardly through a feed leg 4 having a steam sealing chamber 5 to a reactor 0. A plate 'i in the top of reactor 0 provides a bulk supply hopper in the top of the reactor from which the hot solid passes downwardly by feed pipes 8 to provide a compact moving bed in a reaction zone. Ethane is introduced at 9 to 'be distributed across'the bed by inverted angles II from which it passes upwardly through the hot solid countercurrent to movement of the bed to be rapidly heated to the temperature of the granular solid.

A second plate I l separates the ethane reaction zone from a propane reaction zone to which the solids are transferred through feed pipes II. The feed pipes i2 provide a transfer zone of restricted cross section having considerable resistance to gaseous flow and thus forming a boundary be- The zones may be further isolated by steam introduced at I3 and distributed across the bottom of ethane reaction zone by inverted angles ll. The amount of steam introduced at this point may be controlled to give a desired mixture of ethane and steam in the ethane reaction zone since the conversion to olefins appears to proceed better inthe presence of steam. Advantageouslypsteam may be introduced in amounts on the order of 10 to 50% by weight based on the hydrocarbon reactant. The solid is transferred between the zones at a temperature of about 1600 to 1800 F. and a mixture of propane and steam is introduced to the propane reaction zone by line l5 and distributed across the bed by inverted angles ii. If additional cooling of the granular solid'is desired at this point, the charge may be liquid propane and water to further cool by vaporizing the charge. Additional zones of the same type may be provided below the propane reaction zone for The reaction products ,irom the two, or more, reaction zones are combined as shown. The ethane reaction products are withdrawn at port 2i and passed by line}! to a Junction with transfer line 23 connected to the port 2 o! the propane reaction zone. These two streams are combined in pipe I! and quenched by water admitted through pipe 2 and the vaporous mixture is conducted to a tar separator 21 from which heavy material is withdrawn for discard at II. The vapor from separator 21 is passed 'to'a spray condenser 29 having a water spray 3| wherein the vapors are cooled to about 100 F. and transferred to the fractionating system indicated by iractionators ii and 32. The C: fraction from iractionator ii is conveyed to a suitable gas plant for recovery of ethylene while thefraction is advantageously returned'to the propane reaction zone. The liquid separated in spray condenser 29 is transferred to a settler 33 wherein it stratifles to provide an oil layer withdrawn at 34 and a water layer which is cooled in heat exchanger II and recycled, at least in part, to quench line It and spray condenser 29. e

' Returning to the reactor Lpressure responsive elements 81' and 31 are provided to indicate the pressures existing'on either side of the plate ll. These pressure responsive elements are connected to an automatic pressure control 38- which actuates valves 39 and 49 in the discharge lines 22 and 23 respectively. Thus, if the pressure is-lower in the ethane reaction zone than in the propane :zone of restricted cross-section,

-' at a lower temperature in said lower zone, maintaining the pressures in said upper and lower zones adjacent said transfer zone substantially equal, combining the eiiiuent stream from said upper and lower zones, separating a C; out from the combined streams and recycling said out to said lower zone.

LOUIS P. EVANS.

REFERENCES mm The following references are of record in the file .of this patent:

UNITED STATES PATENTS Number Name Date 2,327,175 Conn Aug. 1'7, 1943 2,372,018 Ruthruil Mar. 20, 1945 2,418,673 Sinclair et al Apr. 8, 1947 2,418,679

Utterback Apr. 8, 1947 

